How Can Child With Short Femur In One Leg Walk?

sir, my child(7 Months) suffer from pierry robin syndrom. his right leg is short femer. so right leg is short than left leg in born. i showed a orthopedic doctor(Dr.Niloy Kanti Das- Institute of Child Health), he told us it is a steg by steg operation, it will start after the age of 7 & 8 years, my question is that how can my child walk?